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C I Pogson

Publications and source records attributed to C I Pogson.

At least 91 records · Page 5Linked to original sources
PubMed1981

Factors affecting induction of tyrosine aminotransferase in isolated rat liver cells.

1. The response of tyrosine aminotransferase activity in isolated liver cells has been studied under several conditions. 2. Activity is increased over a 5 h period by both glucagon and glucocorticoids in cells from adrenalectomized rats. The results do not support the view that glucagon action is dependent on preexposure of cells to steroid. 3. In cells from fed animals, significant stimulation is seen only when both glucagon and steroid are present together. 4. In cells from 48 h fasted rats steroid is effective, but glucagon is not significant so. 5. These anomalies are attributed to the differences in hormonal and nutritional status between the animals from which the cells are isolated.

Adrenalectomy↗
PubMed1981

The metabolism of 125I-labelled insulin by isolated Zucker rat hepatocytes.

The metabolism of 125I-labelled insulin by hepatocytes isolated from 48-h-starved Zucker lean and obese rats was studied. Hepatocytes from the lean animals bound significantly more 125I-labelled insulin and had a greater receptor number per cell than did cells from obese littermates. Hepatocytes from the lean animals degraded and internalized more hormone than did those from obese ones. Increased degradation and internalization correlated with the increased receptor number.

Animals↗
PubMed1981

A correlation between in vivo and in vitro effects of the microtubule inhibitors colchicine, parbendazole and nocodazole on myxamoebae of Physarum polycephalum.

The effects of the microtubule inhibitors colchicine, parbendazole and nocodazole on the growth of myxamoebae of Physarum polycephalum were closely paralleled by the effects of these drugs on the assembly in vitro of purified amoebal microtubule protein. Colchicine at 100 microM did not inhibit amoebal growth and did not inhibit formation, or depolymerization, of amoebal microtubules. The benzimidazole carbamate derivatives nocodazole and parbendazole were very effective in both inhibiting growth and inhibiting the assembly in vitro of amoebal microtubule protein. Parbendazole was the most effective.

Benzimidazoles↗
PubMed1980

The metabolism of L-tryptophan by isolated rat liver cells. Quantification of the relative importance of, and the effect of nutritional status on, the individual pathways of tryptophan metabolism.

1. The metabolism of L-tryptophan by liver cells prepared from fed and 48 h-starved rats was studied. Methods are described, with the use of L-[ring-2-(14)C], L-[carboxy-14C]-and L-[benzene-ring-U-14C]-tryptophan, for the simultaneous determination of tryptophan 2,3-dioxygenase and kynureninase activities and of the oxidation of tryptophan to CO2 and non-aromatic intermediates of the kynurenine-glutarate pathway. 2. At physiological concentrations (0.1 mM), tryptophan was oxidized by tryptophan 2,3-dioxygenase at comparable rates in liver cells from both fed and starved rats. Kynureninase activity of hepatocytes from starved rats was 50% greater than that of cells from fed rats. About 10% of the tryptophan metabolized by tryptophan 2,3-dioxygenase was degraded completely to CO2. 3. In the presence of 0.5 mM-L-tryptophan, tryptophan 2,3-dioxygenase and kynureninase activities increased 5--6-fold. Liver cells from starved rats oxidized tryptophan at about twice the rate of these from fed rats. Degradation of tryptophan to non-aromatic intermediates of the glutarate pathway and CO2 was increased only 3-fold, suggesting an accumulation of aromatic intermediates of the kynurenine pathway. 4. Rates of metabolism with 2.5 mM-L-tryptophan were not significantly different from those obtained with 0.5 mM-tryptophan. 5. Rates of synthesis of quinolinic acid from 0.5 mM-L-tryptophan, determined either by direct quantification or indirectly from rates of radioisotope release from L-[carboxy-(14)C]- and [benzene-ring-U-14C]tryptophan, were essentially similar. 6. At all three concentrations examined, tryptophan was degraded exclusively through kynurenine; there was no evidence of formation of either indol-3-ylacetic acid or 5-hydroxyindol-3-ylacetic acid.

Animals↗
PubMed1980

Indoleamine 2,3-dioxygenase. A new, rapid, sensitive radiometric assay and its application to the study of the enzyme in rat tissues.

A simple and convenient assay for indoleamine 2,3-dioxygenase has been developed. This depends on the conversion of D-[ring-2-14C]tryptophan to [14C]formate, excess substrate is removed by adsorption onto charcoal. This assay, which is 20-fold more sensitive than previous procedures, is applicable both to crude extracts and to large numbers of samples. Activity in rat tissues is very much lower than in those of the rabbit; measureable activity is found only in the stomach, spleen, intestine and kidney. Enzyme activity in the rat intestine was increased by 50% in rats pretreated with L-tryptophan.

Adsorption↗
PubMed1980

Identification and characterization of microtubule proteins from myxamoebae of Physarum polycephalum.

Cell extracts of myxamoebae of Physarum polycephalum have been prepared in such a way that they do not inhibit assembly of brain microtubule protein in vitro even at high extract-protein concentration. Co-polymers of these extracts and brain tubulin have been purified to constant stoichiometry and amoebal components identified by radiolabelling. Amoebal tubulin has been identified as having an alpha-subunit, mol.wt. 54 000, which co-migrates with brain alpha-tubulin and a beta-subunit, mol.wt. 50 000, which co-migrates with Tetrahymena ciliary beta-tubulin. Non-tubulin amoebal proteins that co-purify with tubulin during co-polymer formation have been shown to be essential for microtubule formation in the absence of glycerol and appear to be rather more effective than brain microtubule-associated proteins in stimulating assembly. The mitotic inhibitor griseofulvin (7-chloro-2',4,6-trimethoxy-6'-methylspiro[benzofuran-2(3H),1'-cyclohex-2'-ene] -3,4'-dione), which binds to brain microtubule-associated proteins and inhibits brain microtubule assembly in vitro, affected co-polymer microtubule protein in a similar way, but to a slightly greater extent.

Animals↗
PubMed1980

The metabolism of L-tryptophan by isolated rat liver cells. Effect of albumin binding and amino acid competition on oxidatin of tryptophan by tryptophan 2,3-dioxygenase.

1. Novel methods, using L-[ring-2-14C]tryptophan, are described for the measurement of tryptophan 2,3-dioxygenase activity and tryptophan accumulation in isolated rat liver cells. 2. The effects of bovine serum albumin, non-esterified fatty acids and neutral amino acids on tryptophan oxidation by hepatocytes and on the partition of tryptophan between free and albumin-bound forms were investigated. 3. Oxidation of physiological concentrations (0.1 mM) of tryptophan was inhibited by approx. 50% in the presence of 2% (w/v) bovine serum albumin; no effects were found at tryptophan concentrations of 0.5 mM and above. 4. Increases in free tryptophan concentrations produced by displacement of 0.1 mM-tryptophan from albumin-binding sites by palmitate resulted in increased flux through tryptophan dioxygenase. 5. Addition of a mixture of neutral amino acids, at plasma concentrations, to hepatocyte incubations had no effect on the rate of tryptophan oxidation. 6. It is concluded that alterations in free tryptophan concentrations consequent to changes in albumin binding may be an important factor in regulating tryptophan uptake and catabolism by the liver. The results are briefly discussed with reference to possible consequences on brain tryptophan metabolism.

Amino Acids↗
PubMed1980

Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis.

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

Albumins↗
PubMed1980

The influence of the microtubule inhibitor, methyl benzimidazol-2-yl-carbamate (MBC) on nuclear division and the cell cycle in Saccharomyces cerevisiae.

Methyl benzimidazol-2-yl-carbamate (MBC), at a concentration of 100 microM, has a pronounced effect on the growth of Saccharomyces cerevisiae, resulting in the accumulation of cells as large doublets. We have determined a specific execution point for the effect of MBC on the yeast cell cycle, and have shown that this execution point is between the cycle events of spindle pole body duplication and spindle pole body separation. An ultrastructural examination of the MBC-treated cells revealed the absence of cytoplasmic and spindle microtubules. MBC treatment also produced an altered spindle pole body morphology, causing the disappearance of the outer component. Nuclear size was also markedly increased in the MBC-induced doublet cells, although the septa were completely absent from these doublet cells. It is proposed that MBC inhibits microtubule polymerization, rather than causing the depolymerization of stable microtubules.

Benzimidazoles↗